No-rinse chemical foam containing clobetasol propionate, and use thereof in the treatment of psoriasis

ABSTRACT

A self-foaming composition is described that includes clobetasol propionate, for a no-rinse topical application and for application to the skin. The composition can include: at least one intermediate composition B including a gas-generating agent; at least one intermediate composition A including an agent for activating the gas-generating agent; and clobetasol propionate being present in at least one of the intermediate compositions A and B. Also described, is a kit or a single container including a plurality of compartments including such a composition.

CROSS-REFERENCE TO PRIOR APPLICATIONS

This application is a National Stage of PCT/EP2016/073015, filed Sep. 27, 2016, and designating the United States (published on Apr. 6, 2017, as WO 2017/055298 A1), which claims priority under 35 U.S.C. § 119 to French Application No. 1559203, filed Sep. 29, 2015, each hereby expressly incorporated by reference in its entirety and each assigned to the assignee hereof.

The present invention relates to a leave-on topical product in the form of a foam for the pharmaceutical or cosmetic treatment of the skin, and more particularly of psoriasis, and which contains clobetasol propionate.

Psoriasis is one of the commonest skin diseases among all the chronic skin diseases. It essentially causes erythema, desquamation, hyperkeratosis or pruritus and is the cause of severe discomfort for people suffering from this disease. The treatments used to date are based mainly on the application of creams and ointments to the plaques. They contain salicylic acid, local steroids or tar. These treatments are unpleasant, especially the application of tar, and require long applications.

Clobetasol propionate (21-chloro-9-fluoro-11β,17-dihydroxy-16β-methylpregna-1,4-diene-3,20-dione 17-propionate) is a class 1 dermocorticoid, namely a corticoid with very strong activity. Like other cortisone derivatives for local use, it impedes the renewal and multiplication of skin cells. Its efficacy on psoriasis is proven.

There is a need for novel galenical forms for topical application in which clobetasol propionate is stable, well tolerated, efficient and pleasant to apply.

The application of creams and salves is essential in the treatment of psoriasis. These local care products are directed toward reducing squamae and improving the skin comfort and the appearance of the skin. These treatments comprise simple moisturising creams and/or creams to which are added agents that will allow the squamae to be detached more easily, and which are known as keratolytic agents. In all cases, the treatments must provide substantial emollience to make the skin supple.

In the pharmaceutical or cosmetic treatments of these pathologies, products are thus applied to very large areas, and to skin that may be embrittled, but also thickened and difficult to penetrate.

There is thus a need for novel galenical forms and in particular forms of foam or foaming composition type which allow better control of the dose, substantial coverage, and in which clobetasol propionate is stable, well tolerated, efficient and pleasant to apply, especially so as to improve the compliance with the treatment.

The composition according to the invention has the advantage of being in the form of a foam which is generated at the time of use and which is very well tolerated.

After its application, the composition according to the invention is not removed by rinsing.

One of the advantages of the composition of the invention is that it is particularly well tolerated, despite the fact that it is not removed by rinsing, as is shown by the examples illustrating one of the methods of evaluating the tolerance which are presented below.

Various methods exist for evaluating the tolerance of a pharmaceutical or cosmetic product for cutaneous use, among which may be mentioned the in vivo “in used” test or “human patch test” but also the in vitro test, such as the test for measurement of the irritation on Reconstructed Human Epidermis (RHE) described in the OECD TG 439 protocol. The latter method is described in detail in example 3.

Foams or foaming compositions currently exist on the market. However, they all have a certain number of drawbacks:

This is because three types of foams or foaming compositions exist:

-   -   Aerosols, in which the foam is generated by a propellant gas but         with the drawback of being aerosols having the well-known risks         of the latter (contamination and breathing risks in particular).     -   Expanded creams, in which air bubbles are introduced into the         product via a particular manufacturing process. This process has         the drawback of being restricting at the industrial level and         requires major capital expenditure with regard to the packaging         equipment.     -   Foaming formulations which contain foaming surfactants which         generally cause irritation problems arising from the detergent         properties of these foaming surfactants.

Thus, the need therefore remains to develop a pharmaceutical composition, the galenical form of which is different from the known galenical forms, in order, inter alia, to provide compositions intended for topical application containing clobetasol propionate in well-tolerated compositions and thus to overcome the problem of irritation, intended for topical application to human beings, in particular leave-on compositions (i.e. the composition is not removed by rinsing after it has been applied).

The aim of the present invention is thus to provide a composition which meets these needs.

The Applicant has thus developed a novel pharmaceutical composition intended for a leave-on topical application, which is in the form of a foam which advantageously does not contain any foaming surfactant. The term “foaming surfactant” defines surfactants which produce a voluminous, stable and creamy foam when they are mixed with water according to tests that are well known to those skilled in the art.

The following constitute foaming surfactants: anionic surfactants, cationic surfactants, amphoteric surfactants and nonionic surfactants of the family of alkylpolyglucosides and glucamides.

The galenical form according to the invention has the advantage of ensuring good stability of clobetasol propionate. Furthermore, this formulation advantageously results in the production of a mild foam which is fully tolerated and non-irritant, which allows better coverage of the area to be treated and which makes it possible to overcome the problems of tolerance by better control of the dose, by virtue of the spreading properties and the low density of the foam.

Finally, advantageously, this galenical form does not require, for the implementation thereof, the use of propellant gases or aerosols. Thus, “aerosol” or “spray” foams are excluded from the scope of the invention. Likewise, the rinsable foaming compositions of the prior art of standard foaming composition type rich in foaming surfactants and/or the foaming formulations with a reduced content of surfactants but requiring a mechanical foam-generating system (Pulvorex type) are also excluded from the invention. This is likewise the case for foaming compositions involving an expanding process.

Finally, a subject of the present invention is the cosmetic use of the composition according to the invention, by topical application of this composition to the skin, and also a medicament intended for topical application to the skin, comprising such a composition.

A subject of the present invention is also the composition according to the invention, for its use in the treatment of psoriasis.

The present invention will be described in greater detail in the description and the examples hereinbelow.

The composition according to the invention is capable of taking the form of a foam solely by virtue of its composition, and may thus also be defined as a self-foaming composition for topical application.

A first subject of the present invention is consequently a composition containing clobetasol propionate, intended for leave-on topical application, which is provided in the form of a foam, advantageously of semisolid consistency, which advantageously does not contain any foaming surfactant and which comprises a medium that is pharmaceutically compatible with leave-on topical application, in particular to the skin and integuments.

The term “composition in the form of a foam” (also referred to hereinbelow as a self-foaming composition) means a composition of semisolid consistency having an aerated form comparable to a foam.

The self-foaming composition according to the present invention comprises two intermediate compositions or formulations in variable proportions and in particular the ingredients below:

-   -   at least one intermediate composition or formulation A         comprising an agent for activating the gas-generating agent         mentioned below,     -   at least one intermediate composition or formulation B         comprising a gas-generating agent,     -   clobetasol propionate contained in at least one of said         intermediate formulations A and B.

Preferably, the clobetasol propionate is contained in intermediate composition A.

The composition according to the invention is self-foaming, i.e. it foams by simple mixing of the intermediate compositions A and B. A subject of the invention is also the composition in foam form resulting from the mixing of said intermediate compositions A and B.

Depending on the agents present in each intermediate composition (or intermediate formulation), and also on the proportions thereof in said composition, these compositions may be in any galenical form or may have any known texture that may be used in cosmetics and/or in pharmaceuticals for topical application.

Preferably, each intermediate composition (or intermediate formulation) according to the invention may thus be, for example, in the form of gel, emulsion (cream, surfactant-free cream, lotion, milk or fluid cream), serum, solution or suspension, and preferentially in the form of emulsion (cream, surfactant-free cream, lotion, milk or fluid cream) or gel. All of these formulations are included in the context of the invention.

According to the invention, each intermediate composition (or formulation) may have a viscosity (measured at 25° C. and at atmospheric pressure) of between 1 cP and 500 000 cP, advantageously between 500 cP and 350 000 cP, measured with a conventional method of Brookfield RV DV-II type: spindle 6, speed 2.

According to the invention, the term “agent for activating the gas-generating agent” means an ingredient which, by chemical reaction with the gas-generating agent, releases a gas. Preferentially, an acid/base reaction is involved.

According to the invention, the gas generated by the gas-generating agent may be any physiologically compatible gas which allows the production of a foam, for instance carbon dioxide (CO₂) or oxygen (O₂). Preferably, the gas generated from the gas-generating agent is carbon dioxide (CO₂).

According to the invention, since the gas concentration may vary, the amount of bubbles in the composition may vary and may thus give a composition which may range from not very aerated to very strongly aerated.

Thus, according to the invention, the self-foaming composition may preferentially be in any form ranging from aerated to a highly expanded foam.

The composition according to the invention is suitable for topical application and may also comprise a physiologically acceptable medium, i.e. a medium that is compatible with the skin and integuments. It is preferably a cosmetically or pharmaceutically acceptable medium.

In addition, the composition may comprise any active agent that may have activity, optionally therapeutic activity. These active agents may be chosen, inter alia, from emollients, humectants, free-radical scavengers, anti-inflammatory agents, vitamins, depigmenting agents, antiacne agents, antiseborrheic agents, antifungal agents, keratolytic agents, sunscreens, slimming agents and skin-coloring agents.

According to the invention, the composition in foam form (i.e. ready to be applied) has a pH of between 2 and 8, preferentially between 4 and 7.

Insofar as the intermediate composition(s) (or formulation(s)) require storage in at least two compartments for reasons of stability of the ingredients, the present invention relates either to a single compartmentalized container (each compartment receiving one intermediate formulation) and preferably comprising two or three compartments, or to a kit comprising each intermediate formulation stored independently from each other and physically separated.

Intimate extemporaneous mixing (directly on the skin or on any other support) of the intermediate formulations makes it possible to obtain the composition in foam form according to the invention.

More specifically, the intermediate composition (or formulation) A may be in the form of a solution, an emulsion (lotion, cream, emulsifier-free cream, milk or fluid cream) or gel. This composition advantageously contains the agent for activating the gas-generating agent, preferentially an acid, in a sufficient amount (which may be in the form of an acid/base buffer at acidic pH), which may be, as a nonlimiting example, the citric acid/sodium citrate combination.

Formulation B may be in the form of a solution, a gel or an emulsion (lotion, cream, emulsifier-free cream, milk or fluid cream). This composition advantageously contains, in a sufficient amount, a gas-generating agent which may in particular be sodium bicarbonate.

Thus, a subject of the invention is also a kit or a single multi-compartment container as defined previously, for the extemporaneous preparation of a composition in foam form according to the invention, separately comprising at least two intermediate formulations (or intermediate compositions):

-   -   an intermediate formulation A comprising at least one agent for         activating the gas-generating agent; and     -   an intermediate formulation B comprising at least one         gas-generating agent;     -   clobetasol propionate being contained in at least one of said         intermediate formulations A and B.

Preferably, the clobetasol propionate is contained in intermediate composition A.

Gas-Activating Agent:

The agent for activating the gas-generating agent (also referred to as the “gas-activating agent”) is a compound which reacts with the gas-generating agent via a chemical reaction (preferably an acid/base reaction) which releases a gas.

It is advantageously an acid, a partially salified polyacid salt or a buffer solution of a weak acid and of its conjugate base, or a mixture of such compounds.

According to the invention, the acid/base buffer of said acid may be any acid/base buffer of the weak acid, for instance a citric acid/sodium citrate buffer or a tartaric acid/sodium tartrate buffer. Mention will preferably be made of α-hydroxy acids, which are weak acids preferentially with a pKa of between 2 and 6, such as citric acid, tartaric acid, malic acid or lactic acid, but also phosphoric acid and pyrophosphoric acid and optionally the partially salified salts thereof, such as disodium pyrophosphate or sodium dihydrogen phosphate, also known as monosodium phosphate.

Preferentially, according to the invention, the gas-activating agent is chosen from a citric acid/sodium citrate buffer alone, phosphoric acid, sodium phosphate, disodium pyrophosphate, which are alone or as a mixture with the citric acid/sodium citrate buffer.

According to a very preferred embodiment, the gas-activating agent is a citric acid/sodium citrate buffer, alone or as a mixture with sodium phosphate and/or disodium pyrophosphate.

In compositions for sensitive skin or for damaged skin, such as skin affected by psoriasis, the content of citric acid/sodium citrate is preferably less than or equal to 2.4%, relative to the total weight of the intermediate composition A, so as to limit any risk of stinging. In order to improve the tolerance and to avoid the sensation of stinging, preferably, the citric acid/sodium citrate buffer is used as a mixture with disodium pyrophosphate or sodium dihydrogen phosphate.

According to the invention, said gas-activating agent may be present in the intermediate formulation A in an amount that may range from 0.001% to 95% by weight relative to the total weight of the intermediate composition A.

Gas-Generating Agent:

The term “gas-generating agent” means any agent which has the property of generating a gas via a chemical reaction. Mention will be made in this regard of any compound which, when it is mixed with a weak acid, can form a gas via a chemical reaction equivalent to the following: NaHCO₃+RCOOH→RCOONa+H₂O+CO₂

According to the invention, the gas generated from the gas-generating agent present in the intermediate composition B is preferably carbon dioxide (CO₂).

According to the invention, the gas-generating agent is preferably chosen from sodium bicarbonate, potassium bicarbonate, sodium carbonate and potassium carbonate, and mixtures thereof.

Preferentially, according to the invention, the intermediate formulation B comprises an agent which generates carbon dioxide, this agent particularly preferably being sodium bicarbonate.

Said gas-generating agent may be present in the intermediate formulation B in an amount ranging from 1% to 10% by weight and preferentially from 2% to 8% by weight, relative to the weight of the intermediate composition B.

According to the invention, the intermediate formulation A has an acidic pH, advantageously of between 1 and 6, and the intermediate formulation B has a basic pH, advantageously of between 7 and 12.

According to the invention, one or both of the intermediate formulations comprise clobetasol propionate in an amount ranging from 0.0001% to 1%, preferentially from 0.001% to 0.5%, and more preferentially from 0.03% to 0.2% by weight, relative to the weight of the total composition.

In the present description, the term “total composition” or “total formulation” means the composition of the product in foam form after said intermediate compositions have been mixed. Preferably, clobetasol propionate is contained in intermediate composition A which advantageously has an acidic pH in order to optimize its stability.

The intermediate formulation A may be in any galenical form that is compatible with the galenical form desired for the final composition obtained by mixing formulation A with formulation B, and guaranteeing good stability of the clobetasol propionate. The intermediate formulation B may be in any galenical form that is compatible with the galenical form desired for the final composition obtained by mixing formulation B with formulation A. Advantageously, formulation B may be a gel, a solution, a suspension or an emulsion (cream, surfactant-free cream, lotion, milk or fluid cream), preferably an emulsion in order to give maximum emollience.

According to one embodiment of the invention, one of the two intermediate formulations (i.e. intermediate formulation A or intermediate formulation B) is in the form of a gel. In this embodiment, the other intermediate formulation is preferably not in gel form.

Each formulation of the kit or of the multi-compartment container as defined previously in accordance with the invention comprises a physiologically acceptable medium which conveys the compound(s) and which is chosen such that the compounds are capable of reacting with each other to form a self-foaming composition during the mixing of at least the intermediate formulations A and B.

Thus, the extemporaneous mixing of at least two formulations, for example formulation A and formulation B, creates the composition in foam form according to the invention.

During the mixing of the two formulations A and B, the gas-generating agent, such as sodium bicarbonate, may react with the gas-activating agent, such as the acid, and thus give in particular the salt corresponding to the acid, water and CO₂ gas. It is this gas, trapped in the bubbles of the composition, which creates the foam which characterizes the self-foaming composition of the invention.

Thus, by mixing at least intermediate formulation A and intermediate formulation B, the foam composition, referred to as the total composition, according to the invention is obtained.

Unreacted gas-activating agent and/or gas-generating agent may, of course, remain in the composition obtained after mixing at least formulations A and B.

Advantageously, the kit or the single multi-compartment container according to the invention may be designed so that, during the preparation of the composition according to the invention, the intermediate formulations A and B can be mixed in an A/B weight ratio ranging from 0.5 to 2, preferentially from 0.5 to 1.5, more preferentially close to 1 (i.e. from 0.9 to 1.1) and even more preferentially 1. This means that the kit can be designed to simultaneously release doses (by weight) of the intermediate compositions A and B that may be in a weight ratio ranging from 2 doses of B per 1 dose of A to 2 doses of A per 1 dose of B, preferably from 2 doses of B per 1 dose of A to 3 doses of A per 2 doses of B. According to a preferred embodiment of the invention, the kit is designed to simultaneously release 1 dose by weight of A and 1 dose by weight of B.

According to the invention, the kit may be in any form that is compatible with, on the one hand, separate storage of the intermediate formulations A and B and, on the other hand, the ability to perform extemporaneous mixing of A and B.

For example, the intermediate formulations A and B may be packaged in a case with at least two separate compartments, each containing A or B.

According to another aspect, the kit may be in the form of a syringe having at least two separate bodies, each equipped with a piston, said two bodies containing the respective formulations A and B and being designed to simultaneously release, by exerting a force on the piston, the desired doses of A and B.

The invention also relates to a process for preparing a composition according to the invention, characterized in that, in order to obtain the composition in foam form, at least a dose of intermediate formulation A and a dose of intermediate formulation B of the kit as are defined above are mixed extemporaneously in relative weight proportions A/B that may range from 0.5 to 2, preferentially from 0.5 to 1.5 and more preferentially 1.

In order to obtain an optimum foam (final composition), the inventors experimentally sought the optimum contents of gas-generating agent (preferably sodium bicarbonate) and of gas-activating agent (preferably citric acid and/or disodium pyrophosphate and/or sodium dihydrogen phosphate).

Thus, it was determined experimentally that when the gas-activating agent is citric acid, the citric acid/sodium bicarbonate weight ratio in the total composition is between 0.1 and 2, preferentially between 0.5 and 1 and preferably equal to 0.7.

Similarly, it was determined that when the gas-activating agent is disodium pyrophosphate, the disodium pyrophosphate/sodium bicarbonate weight ratio in the total composition is between 0.5 and 5, preferentially between 1 and 3 and preferably equal to 2.4.

Similarly, it was determined that when the gas-activating agent is sodium dihydrogen phosphate, the sodium dihydrogen phosphate monohydrate/sodium bicarbonate weight ratio in the total composition is between 0.5 and 5, preferentially between 1 and 3 and preferably equal to 2.

The sodium bicarbonate/citric acid, sodium bicarbonate/sodium pyrophosphate and sodium bicarbonate/sodium hydrogen phosphate ratios are illustrated in example 4.

Surprisingly, the citric acid/sodium citrate, disodium pyrophosphate or sodium dihydrogen phosphate combination and a gelling system that is compatible with the galenical form made it possible to obtain a formulation with very stable physicochemical properties.

A composition is regarded as being physically stable when its organoleptic characteristics, its pH, its viscosity and the homogeneity of the clobetasol propionate do not change over time under various temperature conditions: room temperature (RT), 30° C. and 40° C. According to the invention, room temperature corresponds to a temperature ranging from 15° C. to 25° C.

A composition is regarded as being chemically stable when the content of active principle it contains does not change over time under various temperature conditions (RT and 40° C.). According to the invention, the composition is regarded as being stable when the content of clobetasol propionate (expressed by weight relative to the weight of the intermediate formulation) is included in the specifications ranging from 90% to 110%.

The composition according to the invention may also comprise one or more agents chosen from dispersants, solubilizers, stabilizers, preserving agents, fatty substances, thickeners, dyes, fragrances, surfactants, gelling agents, complexing agents, neutralizers, foaming emulsifying agents, non-foaming emulsifying agents, fillers, sequestrants, reducing agents, odor maskers, plasticizers, softeners, moisturizers, pigments, clays, mineral fillers, mineral colloids, polymers, proteins, nacreous agents, waxes, oils, for instance paraffins or silicones, fatty acids, solid esters of fatty alcohols or of fatty acids, gums and wetting agents.

Water-soluble dyes, such as FD&C Blue 1 (of empirical formula C₃₇H₃₄N₂Na₂O₉S₃), and liposoluble dyes such as Sudan Red III or Nile Red may also be present in at least one of the intermediate compositions. Such dyes have the advantage of coloring one of the formulation intermediates. This coloring makes it possible to monitor the satisfactory mixing of the two formulation intermediates and to highlight the formation of the foam.

Needless to say, a person skilled in the art will take care to select this or these optional additional adjuvants and/or the amount thereof such that the properties of the active agent(s) that may be added to the composition according to the invention are not, or are not substantially, adversely affected by the envisaged addition.

Gelling Agents for the Intermediate Formulation Comprising the Gas Activator

The intermediate composition A advantageously containing at least one gas-activating agent preferably contains at least one gelling agent and/or suspending agent.

Since formulation A may contain large amounts of acid and of electrolytes, it may prove to be difficult to stabilize. The viscosity and the suspending power of these formulations are often difficult to ensure over time.

As nonlimiting examples of gelling agents and/or suspending agents which are resistant simultaneously to electrolytes and to acidic pH values and which may be included in the compositions A according to the invention, mention may be made of ready-to-use mixtures, such as the ammonium acrylate/acrylamide copolymer & polyisobutene & polysorbate 20 mixture sold by SEPPIC under the name Sepiplus 265®, the acrylamide/sodium acryloyldimethyl taurate copolymer & isohexadecane & polysorbate 80 mixture sold by SEPPIC under the name Simulgel 600 PHA®, the polyacrylate-13 & polyisobutene & polysorbate 20 mixture sold by SEPPIC under the name Sepiplus 400®, the acrylates/C10-30 alkyl acrylate crosspolymer sold by the company Lubrizol under the names Pemulen™ TR-1 Polymeric Emulsifier and Pemulen™ TR-2 Polymeric Emulsifier, polysaccharides with, as nonlimiting examples, xanthan gum, such as Xantural 180® sold by the company Kelco, gellan gum sold under the name Kelcogel® by the company Kelco, sclerotium gum sold under the name Amigel® by Alban Muller Industrie, guar gum and derivatives thereof, such as the hydroxypropyl guar sold under the name Jaguar HP-105® by Rhodia, cellulose and derivatives thereof, such as microcrystalline cellulose and sodium carboxymethyl cellulose sold under the name Blanose CMC 7H4XF® by the company Hercules, hydroxypropylmethylcellulose, in particular the product sold under the name Methocel E4M® Premium by the company Dow Chemical, or hydroxyethylcellulose, in particular the product sold under the name Natrosol HHX 250® by the company Aqualon, the family of the magnesium aluminum silicates, such as Veegum K®, Veegum Plus® or Veegum Ultra® sold by the company Vanderbilt, bentonite sold uner the name Polargel HV®, the family of modified starches, such as the modified potato starch sold under the name Structure Solanace®, the family of carrageenans, in particular divided into four main families: κ, λ, β and ω, such as the Viscarin® and Gelcarin® products sold by the company IMCD. Alternatively, polyvinyl alcohol, also known under the abbreviation PVA, sold by Merck under the name Polyvinyl Alcohol 40-88®. Preferably, Veegum K®, Simulgel 600 PHA® and Xantural 180® will be used alone or in combination in pairs or all three together.

The gelling agent as described above may be used at preferential concentrations ranging from 0.001% to 15% and more preferentially ranging from 0.15% to 5% by weight relative to the weight of the intermediate formulation A.

Gelling Agents for the Intermediate Formulation Containing the Gas Generator

As nonlimiting examples of gelling agents and/or suspending agents and/or gelling agents that are simultaneously resistant to electrolytes and to basic pH values and which may be included in the intermediate compositions B according to the invention, mention may be made of acrylic acid polymers such as the acrylates/C10-30 alkyl acrylate crosspolymer such as the “electrolyte-insensitive” carbomers sold under the name Ultrez 20®, Ultrez 10®, Carbopol 1382® or Carbopol ETD2020NF®, Aqua SF1® sold by the company Lubrizol, the ammonium acrylate/acrylamide copolymer & polyisobutene & polysorbate 20 mixture sold by SEPPIC under the name Sepiplus 265®, the acrylamide/sodium acryloyldimethyl taurate copolymer & isohexadecane & polysorbate 80 mixture sold by SEPPIC under the name Simulgel 600 PHA®, the polyacrylates-13 & polyisobutene & polysorbate 20 mixture sold by SEPPIC under the name Sepiplus 400®, the acrylates/C10-30 alkyl acrylate crosspolymer sold by the company Lubrizol under the names Pemulen™ TR-1 Polymeric Emulsifier and Pemulen™ TR-2 Polymeric Emulsifier, polysaccharides with, as nonlimiting examples, xanthan gum, such as Xantural 180® sold by the company Kelco, gellan gum sold under the name Kelcogel® by the company Kelco, sclerotium gum sold under the name Amigel® by Alban Muller Industrie, guar gum and derivatives thereof, such as the hydroxypropyl guar sold under the name Jaguar HP-105® by Rhodia, cellulose and derivatives thereof, such as microcrystalline cellulose and sodium carboxymethyl cellulose sold under the name Blanose CMC 7H4XF® by the company Hercules, hydroxypropylmethylcellulose, in particular the product sold under the name Methocel E4M® Premium by the company Dow Chemical, or hydroxyethylcellulose, in particular the product sold under the name Natrosol HHX 250® by the company Aqualon, bentonite sold under the name Polargel HV®, the family of the magnesium aluminum silicates, such as Veegum K®, Veegum Plus® or Veegum Ultra® sold by the company Vanderbilt, the family of modified starches, such as the modified potato starch sold under the name Structure Solanace® or the tapioca meal known under the name Naviance Tapioca P® sold by AkzoNobel, or the family of carrageenans, in particular divided into four main families: κ, λ, β and ω, such as the Viscarin® and Gelcarin® products sold by the company IMCD. Preferably, Veegum K®, Simulgel 600 PHA® and Xantural 180® will be used alone or in combination in pairs or all three together.

The gelling agent as described above may be used at preferential concentrations ranging from 0.001% to 15% and more preferentially ranging from 0.15% to 5% by weight relative to the weight of the intermediate formulation B.

Humectants

Among the humectants and/or emollients which may act as skin moisturizer and facilitate the application of the formulation, use is optionally made, without this list being limiting, of compounds such as a polyol that is water-miscible at room temperature (25° C.) chosen especially from sugars (for example glucose or lactose), polyethylene glycols (PEG) (for example Lutrol E400®), urea, and amino acids (for example serine, citrulline, arginine, asparagine or alanine).

As preferred humectant and/or emollient, mention may be made of glycerol.

The humectants may be used, alone or in combination, at preferential concentrations ranging from 0.001% to 50% and more preferentially ranging from 0.01% to 30% by weight relative to the weight of the total formulation.

Chelating Agents

Among the chelating agents, mention may be made, as nonlimiting examples, of ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), ethylenediaminebis(O-hydroxyphenylacetic acid) (EDDHA), hydroxy-2-ethylenediaminetriacetic acid (HEDTA), ethyldiaminebis(O-hydroxy-p-methylphenyl)acetic acid (EDDHMA) and ethylenediaminebis(5-carboxy-2-hydroxyphenyl)acetic acid (EDDCHA).

As preferred chelating agent, mention may be made of ethylenediaminetetraacetic acid (EDTA) sold especially under the name Titriplex III®; it may be used at preferential concentrations ranging from 0.001% to 1% and more preferentially from 0.05% to 0.1% by weight relative to the weight of the total formulation.

Solvent and Pro-Penetrating Agent

Compositions A and B may contain one or more pro-penetrating agents, which facilitate the penetration of the active principles and allow the dissolution of the active principle present in the composition according to the invention. More particularly, it is chosen from C1-C4 volatile alcohols, such as ethanol or isopropanol, which may be included in the composition at up to 10% by weight of the intermediate composition A.

Use may also be made of polyols especially containing from 2 to 20 carbon atoms, preferably containing from 2 to 10 carbon atoms and preferentially containing from 2 to 6 carbon atoms, such as propylene glycol, butylene glycol, pentylene glycol, hexylene glycol, dipropylene glycol, diethylene glycol, 1,3-propylene glycol sold under the name Zemea by the company DuPont Tate & Lyle Bio Products Company, LLC, and mixtures thereof. The preferred glycol is propylene glycol, which may be present in the intermediate composition A at up to 50% or more preferentially up to 25% by weight. Alternatively, the solvent and pro-penetrating agent may be chosen from glycol ethers, such as ethoxydiglycol sold by Gattefossé under the name Transcutol HP. It may be included in composition A in a content ranging from 0.1% to 10% and more preferentially between 0.5% and 2% by weight relative to the weight of the intermediate formulation A.

Excipients with Specific Properties

The composition according to the invention may contain one or more cosmetic active agents, for instance, as nonlimiting examples, allantoin with anti-irritant properties, dipotassium glycyrrhizate for its anti-inflammatory properties, salicylic acid and coal tars with keratolytic properties, capsaicin which attenuates itching, or alternatively cicatrizing α-bisabolol.

Fillers and Particles

Fillers and/or particles may be used to stabilize and boost the foam. Some of them have the specific property of being positioned at the water/air interface and of thus stabilizing this interface. Fillers that may be mentioned include talc, metal oxides such as zinc oxide, titanium dioxide TiO2 T2000 sold by the company Merck under the name Eusolex® T-2000, clays such as Laponites®, Bentones® or Bentonites®, but also cellulose ethers such as Methocel K100 LV® sold by the company Dow, silicas such as Aerosil® R972 sold by the company Evonik or Silice HDK® H13L sold by Wacker. They may be used at concentrations ranging from 0.01% to 10% by weight relative to the weight of the total formulation.

Preserving Agent:

Examples of preserving agents that may be mentioned include benzalkonium chloride, bronopol, chlorhexidine, chlorocresol and derivatives thereof, ethyl alcohol, phenoxyethanol, potassium sorbate, diazolidinyl urea, benzyl alcohol, parabens and sodium benzoate, or mixtures thereof.

As preferred preserving system, mention may be made of the combination of phenoxyethanol and pentylene glycol or sodium benzoate.

Oils of the Fatty Phase

The composition according to the invention may also comprise a fatty phase. This fatty phase may be present in one and/or the other of the intermediate compositions A and B. Depending on the galenical form of the intermediate formulations, the fatty phase may represent from 0% to 95% by weight relative to the weight of each intermediate formulation.

The fatty phase of the composition according to the invention may comprise, for example, plant, mineral, animal or synthetic oils, silicone oils, and mixtures thereof.

As examples of mineral oils, mention may, for example, be made of liquid paraffins of various viscosities, such as Primol 352®, Marcol 82® and Marcol 152® sold by the company Esso.

As plant oils, mention may be made of sweet almond oil, palm oil, soybean oil, sesame oil, sunflower oil and olive oil.

As animal oils or the substitute thereof of plant origin, mention may be made of lanolin, squalene, fish oil with, as a derivative, the perhydrosqualene sold under the name Sophiderm® by the company Sophim.

As synthetic oils, mention may be made of an ester such as cetearyl isononanoate, for instance the product sold under the name Cetiol SN PH® by the company Cognis France, isononyl isononanoate such as Dub ININ® sold by the company Stéarineries Dubois, isopropyl myristate sold under the name Crodamol IPM by the company Croda, diisopropyl adipate, for instance the product sold under the name Crodamol DA® by the company Croda, isopropyl palmitate, for instance the product sold under the name Crodamol IPP® by the company Croda, and caprylic/capric triglyceride, such as Miglyol 812® sold by the company Univar. As hydrogenated polyisobutenes, mention may be made of the Parleam® products sold by the company Rossow, the C12-15 alkyl benzoate sold under the name Crodamol AB by the company Croda, octyldodecanol or Eutanol G sold by the company BASF, oleyl alcohol sold under the name Kollicream OA by the company BASF, PPG-11 Stearyl Ether or Arlamol P511E sold by the company Croda.

As silicone oils, mention may be made of a dimethicone, for instance the product sold under the name Q7-9120 Silicone Fluid® with a viscosity from 20 cSt to 12 500 cSt, by the company Dow Corning, or a cyclomethicone, for instance the product sold under the name ST-Cyclomethicone 5NF®, also by the company Dow Corning.

These oils may be present, alone or in combination, in contents ranging from 0.5% to 50% by weight, and preferentially from 2% to 30% by weight relative to the weight of the total composition.

Nonliquid Fatty Substances

The composition according to the invention, and in particular the intermediate formulation B, may also comprise solid fatty substances such as natural or synthetic waxes, fatty acids such as stearic acid, fatty alcohols such as Speziol C18® Pharma or Speziol C16® sold by the company Cognis, and texturing agents of tribehenate type, such as Compritol 888® sold by the company Gattefosse or hydrogenated castor oils such as Cutina HR® sold by the company Cognis or glyceryl stearate such as Geleol® sold by the company Gattefosse or DC 9045 Elastomer Blend® sold by the company Dow Corning.

These nonliquid fatty substances may be used alone or as a mixture from 0% to 30% by weight relative to the weight of the total formulation. However, exceptional foam quality has been observed when fatty alcohols of formula CH3(CH2)nOH (n is between 11 and 23) are present in contents of greater than 1% by weight relative to the weight of the total formulation.

Nonionic Emulsifiers

The composition according to the invention, and especially the intermediate formulation B, may also comprise one or more nonionic emulsifiers.

Preferred emulsifiers that may be mentioned include hydrophilic emulsifiers such as glyceryl stearate (and) PEG-100 stearate sold under the name Arlacel 165FL® by the company Uniqema, lipophilic emulsifiers such as Glucate SS® and Glucamate SSE®, polyoxyethylene (21) stearyl ether sold under the name Brij 721® by the company Uniqema or also in the same family Brij S2® and Brij S20®. The self-emulsifying wax sold by Croda under the name of Polawax NF®. Mention may also made of nonionic surfactants with a high HLB, sorbitan esters such as POE (20) sorbitan monooleate sold under the name Tween 80® (HLB=15), POE (20) sorbitan monostearate sold under the name Tween 60® (HLB=14.9), fatty alcohol ethers such as POE (21) stearyl ether (HLB=15.5), or ceteareth-20 sold under the name of Eumulgin B2 PH® by Cognis (HLB of 15.5), or nonionic surfactants with a low HLB, sorbitan esters, such as sorbitan monostearate (sold under the name of Span 60® by Uniqema), glycerol esters such as glyceryl monostearate (Cutina GMS® from Cognis), sucrose esters with a low HLB, such as sucrose distearate. In another form according to the invention, the surfactants that may be used are polyglycerol esters. They are esters of polyglycerolated fatty acids obtained by condensation of glycerol. Glycolipid emulsifiers, such as Montanov 202® sold by the company SEPPIC. Some emulsifiers may be sold in the form of a mixture, such as Emulium Kappa® and Emulium Delta® sold by Gattefosse. These surfactants may be used, alone or as a mixture, so that the HLB of the system is greater than 11 and preferentially greater than 15.

Such emulsifiers may be used at between 0.01% and 30% by weight, relative to the weight of the total composition, preferentially between 0.1% and 15% and more preferentially between 0.5% and 7%.

The examples that follow illustrate the invention without limiting its scope.

EXAMPLES Example 1: Formulation Examples Formulation Example A: Intermediate Compositions Containing the Gas-Activating Agent, Formulated with an Acidic pH

Intermediate formulations A were prepared according to the following process:

Step 1: At a temperature above 60° C., add the gelling agents and then the gas-generator activating agent(s) with stirring to the main water phase.

Step 2: In parallel, prepare the active phase by dissolving the clobetasol propionate in the solubilizing/pro-penetrating agent.

Step 3: At a temperature below 30° C., add the active phase to the main phase.

Step 4: Add the additives and the preserving agents, cosmetic active agents and chelating agents.

In the formulation examples below, the amounts are expressed relative to the weight of the intermediate formulation rather than relative to the weight of the total formulation.

Example A1

INCI Name % by weight WATER QS 100 GLYCEROL 8 MAGNESIUM ALUMINUM SILICATE 1 XANTHAN GUM 0.5 CETOSTEARYL ALCOHOL 3 CYCLOPENTASILOXANE 2 CETEARETH-20 3 GLYCERYL DIBEHENATE 3 PPG-11 STEARYL ETHER 20 PHENOXYETHANOL 1 CLOBETASOL PROPIONATE 0.1 DISODIUM EDTA 0.1 ETHOXYDIGLYCOL 1.2 CITRIC ACID 1.75 SODIUM CITRATE 1.3 SODIUM PYROPHOSPHATE 6 POLOXAMER 124 0.2

Example A2

INCI Name % by weight WATER QS 100 GLYCEROL 8 MAGNESIUM ALUMINUM SILICATE 1 XANTHAN GUM 0.5 CETOSTEARYL ALCOHOL 3 CYCLOPENTASILOXANE 2 CETEARETH-20 3 GLYCERYL DIBEHENATE 3 MINERAL OIL 24 PHENOXYETHANOL 1 CLOBETASOL PROPIONATE 0.1 ETHANOL 10 PHENOXYETHANOL 1 DISODIUM EDTA 0.1 CITRIC ACID 3.5 SODIUM CITRATE 2.7

Example A3

INCI Name % by weight WATER QS 100 GLYCEROL 8 MAGNESIUM ALUMINUM SILICATE 1 XANTHAN GUM 0.5 CETOSTEARYL ALCOHOL 3 CYCLOPENTASILOXANE 2 CETEARETH-20 3 GLYCERYL DIBEHENATE 3 CAPRYLIC/CAPRIC TRIGLYCERIDE 24 PHENOXYETHANOL 1 CLOBETASOL PROPIONATE 0.1 PROPYLENE GLYCOL 30 PHENOXYETHANOL 1 DISODIUM EDTA 0.1 CITRIC ACID 1.7 SODIUM CITRATE 1.3 DISODIUM PYROPHOSPHATE 6

Example A4

INCI Name % by weight WATER QS 100 GLYCEROL 8 MAGNESIUM ALUMINUM SILICATE 1 XANTHAN GUM 0.5 CLOBETASOL PROPIONATE 0.1 PROPYLENE GLYCOL 30 PHENOXYETHANOL 1 DISODIUM EDTA 0.1 CITRIC ACID 1.7 SODIUM CITRATE 1.3 DISODIUM PYROPHOSPHATE 6

Example A5

INCI Name % by weight WATER QS 100 GLYCEROL 8 MAGNESIUM ALUMINUM SILICATE 1 XANTHAN GUM 0.5 CLOBETASOL PROPIONATE 0.1 ETHANOL 10 PHENOXYETHANOL 1 DISODIUM EDTA 0.1 CITRIC ACID 1.7 SODIUM CITRATE 1.3 DISODIUM PYROPHOSPHATE 6

Formulation Example B: Intermediate Compositions Comprising the Gas-Generating Agent, Formulated with a Basic pH

The intermediate formulations were prepared according to the following process:

Step 1′: At a temperature above 60° C., add the gelling agents with stirring to the main water phase.

Optional step 2′: In parallel, heat the fatty phase (containing the oils, the waxes and the surfactants) to a temperature above 60° C.

Optional step 3′: At a temperature above 60° C., prepare the emulsion by adding the fatty phase to the main phase.

Step 4′: Add the additives such as the preserving agents or ethanol at a temperature suitable for the additive.

Step 5′: Neutralize the mixture.

Step 6′: At a temperature below 40° C., add the sodium bicarbonate.

Example B1

INCI Name % by weight WATER QS 100 MAGNESIUM ALUMINIUM SILICATE 2.5 XANTHAN GUM 0.6 TRIETHANOLAMINE 1.2 SODIUM HYDROGEN CARBONATE 5 PHENOXYETHANOL 0.8

Example B2

INCI Name % by weight WATER QS 100 MAGNESIUM ALUMINUM SILICATE 2.5 XANTHAN GUM 0.5 CETEARETH-20 3 CETOSTEARYL ALCOHOL 3 GLYCERYL DIBEHENATE 3 CAPRYLIC/CAPRIC TRIGLYCERIDE 10 DL-α-TOCOPHEROL 0.05 MINERAL OIL 5 COCONUT (COCOS NUCIFERA) OIL 2 PRUNUS AMYGDALUS DULCIS 5 CYCLOPENTASILOXANE 3 SODIUM HYDROXIDE 0.09 PHENOXYETHANOL 0.8 SODIUM HYDROGEN CARBONATE 5

Example B3

INCI Name % by weight WATER QS 100 MAGNESIUM ALUMINUM SILICATE 2.5 XANTHAN GUM 0.5 CETEARETH-20 3 CETOSTEARYL ALCOHOL 3 GLYCERYL DIBEHENATE 3 CAPRYLIC/CAPRIC TRIGLYCERIDE 10 DL-α-TOCOPHEROL 0.05 MINERAL OIL 2 PRUNUS AMYGDALUS DULCIS 5 CASTOR OIL 2 DIMETHICONE 3 SODIUM HYDROXIDE 0.09 PHENOXYETHANOL 0.8 SODIUM HYDROGEN CARBONATE 5

Example B4

INCI Name % by weight WATER QS 100 MAGNESIUM ALUMINUM SILICATE 2.5 XANTHAN GUM 0.5 CETEARETH-20 3 CETOSTEARYL ALCOHOL 3 GLYCERYL DIBEHENATE 3 CAPRYLIC/CAPRIC TRIGLYCERIDE 10 DL-α-TOCOPHEROL 0.05 SHEA BUTTER 3 PRUNUS AMYGDALUS DULCIS 5 DIMETHICONE 2 SODIUM HYDROXIDE 0.09 PHENOXYETHANOL 0.8 SODIUM HYDROGEN CARBONATE 5

INCI Name % by weight WATER QS 100 MAGNESIUM ALUMINUM SILICATE 2.5 XANTHAN GUM 0.5 CETEARETH-20 3 CETOSTEARYL ALCOHOL 3 GLYCERYL DIBEHENATE 3 CAPRYLIC/CAPRIC TRIGLYCERIDE 6 SODIUM HYDROXIDE 0.09 PHENOXYETHANOL 0.8 SODIUM HYDROGEN CARBONATE 5

Example B5

The mixtures in a 1:1 weight ratio of the intermediate compositions A and B described above are represented in the table below. A cross at the intersection of two formulation intermediates indicates that the mixture was tested and generated a foam having the desired properties.

Formulation B Formulation A B1 B2 B3 B4 B5 A1 X X X X X A2 X X X X X A3 X X X X X A4 X X X X A5 X X X X

Example 2: Foam Density

From the formulation examples described in example 1, foam density measurements were taken at the moment of contact of the two intermediate formulations A and B (T0) and then when the chemical reaction generated by bringing the two compositions into contact is complete. These studies showed that the final composition is in the form of a foam with a suitable density.

Example 3: Comparative Study of Measurement of Irritation

Study Protocol.

A study was performed according to the OECD TG 439 protocol in force for the short application time (RHE/product contact time 15 min). This protocol was appropriate for a long application time (RHE/product contact time 18 h).

The objective of this study is to evaluate the tolerance of the supports of the complete and intermediate formulations on reconstructed human epidermides (RHE, Episkin model) through:

-   -   evaluation of the reduction of MTT (cell viability)     -   measurement of the release of IL-1alpha (irritation marker)

The formulations tested are:

-   -   An intermediate composition of acidic formulation placebo (i.e.         not containing clobetasol propionate),     -   An intermediate composition of basic formulation     -   The complete formulation composed of the mixture of the acidic         formulation placebo+the basic formulation (in a 50/50 weight         ratio),     -   A commercial reference in the form of topical product.

This study showed that all the formulations tested are non-irritant.

Example 4

The ideal content of citric acid, sodium pyrophosphate and sodium dihydrogen phosphate monohydrate to react with 5% of sodium bicarbonate was established empirically. The values are expressed as weight/weight percentages relative to the weight of each of the two intermediate formulations.

Ratio 1 Ratio 2 Ratio 3 Sodium bicarbonate  5% 5%  5% Citric acid 3.5% — — Disodium pyrophosphate — 12 — Sodium dihydrogen — 7.2% phosphate monohydrate

In order for the pH of the formulation containing the gas activator to have optimum compatibility with the skin, sodium citrate was added so as to create a citric acid/sodium citrate buffer.

Part of the citric acid/sodium citrate buffer may advantageously be replaced with disodium pyrophosphate and vice versa like the contents cited by way of example in table I below:

TABLE III the values are expressed as weight/weight percentages relative to the weight of each of the two intermediate formulations. E 1 E2 E 3 E 4 E 5 E 6 E 7 Sodium  5% 5%  5%  5%  3%   3%  3% bicarbonate Citric acid 3.5% 1.75%   1.4% 0 2.1% 1.05% 0 Sodium citrate 2.7% 1.3%   1% 0 1.6% 1.15% 0 Disodium pyrophosphate 0 6% 7.2% 12% 0  3.6% 7.2%

Part of the citric acid/sodium citrate buffer may advantageously be replaced with sodium dihydrogen phosphate monohydrate and vice versa, like the contents cited by way of example in table IV below:

TABLE IV the values are expressed as weight/weight percentages relative to the weight of each of the two intermediate formulations. E1 E8 E9 Sodium bicarbonate  5%  5%  5% Citric acid 3.5% 1.5% 0 Sodium citrate 2.7% 0.5% 0 Sodium dihydrogen 0 6.2% 10% phosphate monohydrate

In one particular embodiment, it was determined that when the amount of citric acid is greater than or equal to 1.4, the amount of foam is optimal when disodium pyrophosphate is present in the composition according to the following equation: [C]=2.4[B]−2.4[A]/0.7

when:

[C]=weight content of disodium pyrophosphate in the intermediate composition A

[A]=weight content of citric acid monohydrate in the intermediate composition A

[B]=weight content of sodium bicarbonate in the intermediate composition B

The above equation thus makes it possible to calculate the optimum contents between sodium bicarbonate, citric acid and sodium pyrophosphate. 

The invention claimed is:
 1. A self-foaming leave-on topical composition, comprising: (a) at least one intermediate composition B comprising (i) 1% to 10% by weight, relative to the weight of the intermediate composition B, of a gas-generating agent selected from the group consisting of sodium bicarbonate, potassium bicarbonate, sodium carbonate and potassium carbonate, and mixtures thereof, and (ii) a gelling agent and/or suspending agent; (b) at least one intermediate composition A comprising (i) 0.001% to 95% by weight, relative to the total weight of the intermediate composition A, of an agent for activating the gas-generating agent comprising a citric acid/sodium citrate buffer and sodium dihydrogen phosphate and/or disodium pyrophosphate, and (ii) a gelling agent and/or suspending agent; and (c) 0.001% to 0.5% of clobetasol propionate by weight, relative to the weight of the composition comprising intermediate compositions A and B, wherein the clobetasol propionate is present in intermediate composition A and/or B; and wherein the gas-generating agent of intermediate composition B and the agent for activating the gas-generating agent of intermediate composition A react to produce carbon dioxide gas upon mixing.
 2. The composition as claimed in claim 1, wherein the clobetasol propionate is present in the intermediate composition A.
 3. The composition as claimed in claim 1, wherein the composition does not comprise any foaming surfactants selected from the group consisting of anionic surfactants, cationic surfactants, amphoteric surfactants and nonionic surfactants of the family of alkylpolyglucosides and glucamides.
 4. The composition as claimed in claim 1, wherein the intermediate composition B has a pH of from 7 to
 12. 5. The composition as claimed in claim 1, wherein the citric acid/sodium citrate buffer is present in the intermediate composition A in an amount of less than or equal to 2.4% by weight, relative to the weight of the intermediate composition A.
 6. The composition as claimed in claim 1, wherein the intermediate composition A has an acidic pH.
 7. The composition as claimed in claim 1, wherein the intermediate composition A is in the form of a solution, a gel or an emulsion.
 8. The composition as claimed in claim 1, wherein the intermediate composition B is in the form of a solution, a gel or an emulsion.
 9. A composition in foam form, wherein the composition is obtained by mixing of the intermediate compositions A and B as claimed in claim
 1. 10. The composition as claimed in claim 1, wherein the composition further comprises one or more active agents selected from the group consisting of emollients, humectants, free-radical scavengers, anti-inflammatory agents, vitamins, depigmenting agents, antiacne agents, antiseborrheic agents, antifungal agents, keratolytic agents, sunscreens, slimming agents and skin-coloring agents.
 11. The composition as claimed in claim 1, wherein the composition further comprises one or more agents selected from the group consisting of dispersants, solubilizers, stabilizers, preserving agents, fatty substances, thickeners, dyes, fragrances, gelling agents, complexing agents, neutralizers, non-foaming emulsifying agents, fillers, sequestrants, reducing agents, odor maskers, plasticizers, softeners, moisturizers, pigments, clays, mineral fillers, mineral colloids, polymers, proteins, nacreous agents, propellants, waxes, oils, for instance paraffins, fatty acids, solid esters of fatty alcohols or of fatty acids, gums and wetting agents.
 12. A method for treating psoriasis, comprising administering an effective amount of the composition as claimed in claim 1, to the skin of an individual in need thereof.
 13. A kit or single multi-compartment container separately comprising: (a) an intermediate composition B comprising (i) 1% to 10% by weight, relative to the weight of the intermediate composition B, of at least one gas-generating agent selected from the group consisting of sodium bicarbonate, potassium bicarbonate, sodium carbonate and potassium carbonate, and mixtures thereof, and (ii) a gelling agent and/or suspending agent; and (b) an intermediate composition A comprising (i) 0.001% to 95% by weight, relative to the total weight of the intermediate composition A, of at least one agent for activating the gas-generating agent, comprising a citric acid/sodium citrate buffer and sodium dihydrogen phosphate and/or disodium pyrophosphate, and (ii) a gelling agent and/or suspending agent; wherein clobetasol propionate is present at a concentration of between 0.001% and 0.5% by weight, relative to the weight of the composition comprising intermediate compositions A and B; wherein the clobetasol propionate is present in intermediate composition A and/or B; and wherein the gas-generating agent of intermediate composition B and the agent for activating the gas-generating agent of intermediate composition A react to produce carbon dioxide gas upon mixing.
 14. The kit or single multi-compartment container as claimed in claim 13, wherein the kit or single multi-compartment container is designed for mixing the intermediate compositions A and B in an A/B weight ratio ranging from 0.5 to
 2. 15. A process for preparing a self-foaming composition, the process comprising formulating the composition for a leave-on topical application comprising clobetasol propionate, by mixing the intermediate composition A as defined in claim 1 with the intermediate composition B as defined in claim 1, in relative weight proportions A/B ranging from 0.5 to
 2. 16. The composition as claimed in claim 3, wherein the composition does not comprise any foaming surfactants.
 17. The composition as claimed in claim 1, wherein the gas-generating agent is sodium bicarbonate.
 18. The composition as claimed in claim 1, wherein the gas-generating agent is present in the intermediate composition B in an amount ranging from 2% to 8% by weight.
 19. The composition as claimed in claim 4, wherein the pH is basic.
 20. The composition as claimed in claim 6, wherein the acidic pH is from 1.0 to 6.0.
 21. The composition as claimed in claim 7, wherein the intermediate composition A is in the form of a gel.
 22. The composition as claimed in claim 8, wherein the intermediate composition B is in the form of a gel or an emulsion.
 23. The kit or single multi-compartment container as claimed in claim 14, wherein the A/B weight ratio is from 0.5 to 1.5.
 24. The kit or single multi-compartment container as claimed in claim 14, wherein the A/B weight ratio is from 0.9 to 1.1.
 25. The kit or single multi-compartment container as claimed in claim 14, wherein the A/B weight ratio is
 1. 26. The process as claimed in claim 15, wherein the A/B weight proportion ranges from 0.5 to 1.5.
 27. The process as claimed in claim 15, wherein the A/B weight proportion is
 1. 28. The composition of claim 1, wherein the clobetasol propionate is present at a concentration of 0.2% to 0.5% by weight, relative to the weight of the composition comprising intermediate compositions A and B.
 29. The composition as claimed in claim 1, wherein: the gas generating agent is sodium bicarbonate; the agent for activating the gas-generating agent comprises citric acid/sodium citrate buffer and disodium pyrophosphate; the citric acid is present in the intermediate composition A at a concentration of greater than or equal to 1.4% by weight, relative to the weight of the intermediate composition A; and the concentrations of sodium bicarbonate, citric acid, sodium citrate, and disodium pyrophosphate satisfy the following relationship: [C]=2.4[B]−2.4[A]/0.7, wherein: [C]=concentration of disodium pyrophosphate by weight, relative to the weight of the intermediate composition A; [A]=concentration of citric acid by weight, relative to the weight of the intermediate composition A; and [B]=concentration of sodium bicarbonate by weight, relative to the weight of the intermediate composition B.
 30. The composition as claimed in claim 1, wherein clobetasol propionate is the sole active agent. 